The invention herein relates to polyurethane foams, particularly of the type suitable for use as thermal insulation.
Polyurethane foams used for thermal insulation may in many field uses be subject to burning. These foams are commonly rated for combustion hazard properties by a standard test known as the "tunnel test" and described in ASTM Standard Test Method E-84, "Surface Burning Chracteristics of Building Materials." Polyurethane foams normally have flame spread ratings in this test of less than 25, which is considered to be a good rating. On the other hand, conventional polyurethane foams normally have smoke generation ratings in this test in the range of 100 to 200, which represents major amounts of smoke generation. Since when a fire occurs where polyurethane insulation is being used this excessive smoke generation can present a major hazard to fire fighting efforts, it would be very desirable to have a polyurethane foam which has a low smoke generation rating (defined as less than 50 in the tunnel test).